High Temperature Acclimation Research Articles

Time course of acclimation of critical thermal limits in two springtail species (Collembola)

Critical thermal limits are one of the most important sources of information on the possible impacts of climate change on soil microarthropods. The extent of plasticity of tolerance limits can provide valuable insights about the likely responses of ectotherms to environmental change. Although many studies have investigated various aspects of the acclimatory response of thermal limits to temperature changes in arthropods, the number of studies focusing on the temporal dynamics of this plastic response is relatively small. Collembola, one of the key microarthropods groups in almost all soil ecosystems around the world, have been the focus of several thermal acclimation studies. Yet the time course of acclimation and its reversal have not been widely studied in this group. Here we investigated the time course of acclimation of critical thermal maxima (CTmax) and minima (CTmin) of two springtail species. We exposed a Cryptopygus species from temperate southern Australia to high and low temperature conditions and Mucrosomia caeca from Sub-Antarctic Macquarie Island to high temperature conditions. Upper thermal limits in both species were found to be highly constrained, as CTmax did not show substantial response to high and low temperature acclimation both in the Cryptopygus species and M. caeca, whereas CTmin showed significant responses to high and low temperature conditions. The acclimation begins to stabilize in approximately seven days in all treatments except for the acclimation of CTmin under high temperature conditions, where the pattern of change suggests that this acclimation might take longer to be completed. Although reversal of this acclimation also begins to stabilize under 7 days, re-acclimation was relatively slow as we did not observe a very clear settling point in 2 of the 3 re-acclimation treatments. The observed limits on the plasticity of CTmax indicate that both of these species may be very limited in their ability to respond plastically to short-term rapid changes in temperature (i.e temperature extremes).

Wheat 2-Cys peroxiredoxin plays a dual role in chlorophyll biosynthesis and adaptation to high temperature.

The molecular mechanism of high-temperature stress (HTS) response, in plants, has so far been investigated using transcriptomics, while the dynamics of HTS-responsive proteome remain unexplored. We examined the adaptive responses of the resilient wheat cultivar 'Unnat Halna' and dissected the HTS-responsive proteome landscape. This led to the identification of 55 HTS-responsive proteins (HRPs), which are predominantly involved in metabolism and defense pathways. Interestingly, HRPs included a 2-cysteine peroxiredoxin (2CP), designated Ta2CP, presumably involved in stress perception and adaptation. Complementation of Ta2CP in yeast and heterologous expression in Arabidopsis demonstrated its role in thermotolerance. Both Ta2CP silencing and overexpression inferred the involvement of Ta2CP in plant growth and chlorophyll biosynthesis. We demonstrated that Ta2CP interacts with protochlorophyllide reductase b, TaPORB. Reduced TaPORB expression was found in Ta2cp-silenced plants, while upregulation was observed in Ta2CP-overexpressed plants. Furthermore, the downregulation of Ta2CP in Taporb-silenced plants and reduction of protochlorophyllide in Ta2cp-silenced plants suggested the key role of Ta2CP in chlorophyll metabolism. Additionally, the transcript levels of AGPase1 and starch were increased in Ta2cp-silenced plants. More significantly, HTS-treated Ta2cp-silenced plants showed adaptive responses despite increased reactive oxygen species and peroxide concentrations, which might help in rapid induction of high-temperature acclimation.

Importance of experienced thermal history: Effect of acclimation temperatures on the high-temperature tolerance and growth performance of juvenile marbled flounder.

Experienced thermal history often affects the temperature tolerance of fish; however, the effect of thermal history on growth performance is unclear. To contribute to effective stocking (release of hatchery-reared juveniles in the field), we conducted four laboratory experiments using juvenile marbled flounder (Pseudopleuronectes yokohamae, around 30mm standard length and 0.3g body wet weight) acclimated at 12°C and 24°C for approximately 2 weeks to investigate the effects of acclimation temperature on high-temperature tolerance, food consumption, and growth performance. The acclimation to 24°C increased tolerance to high temperatures, as shown in a 24-h exposure experiment and in a temperature elevation experiment. The 50% lethal temperature (upper incipient lethal temperature) was estimated to be 25.9°C and 29.0°C for the 12°C and 24°C acclimation groups, respectively. In subsequent experiments, we tested the effects of high and low temperature acclimation on the food consumption and growth performance of two size groups of juveniles (28.7±2.0 and 34.5±2.9mm, mean±SD), that were reared at temperatures ranging from 14°C to 23°C. The optimal temperature for growth was 20°C and did not differ between the acclimation temperatures or between the size groups. However, food consumption and growth performance were suppressed by acute temperature changes. Specifically, feeding and growth were lower in the 24°C-acclimated group than in the 12°C-acclimated group when exposed to 14°C, which is close to the natural water temperature at release in the field. These results suggest that experienced thermal history does not affect the optimal temperature but can affect the growth performance of juveniles. To maximize the post-release growth of hatchery-reared juveniles, the influence of thermal history should be taken into consideration and acute thermal changes before release should be avoided.

Thermal preferences of two spider species: an orb-web weaver and a synanthropic funnel-web weaver

Temperature, an important factor in the ecological niche, determines the individual fitness, distribution and abundance of many spider species. Typically, spiders from different habitats have different thermal preferences, which vary depending on the season, time of day, and reproductive status. Selected temperatures may also depend on thermal acclimation of animals. The study aimed at determining preferred temperatures of females of two spider species, synanthropic Eratigena atrica and garden Araneus diadematus, exposed to low (14°C) and high (23°C) acclimation temperatures. The mean preferred temperature observed in a thermal gradient varied between the species: E. atrica selected 13.7 ± 1.0°C, while A. diadematus selected 22.5 ± 1.5°C, irrespective of the acclimation temperature. Accordingly, thermal niche overlaps between the species were significantly lower than predicted by the random distribution. E. atrica changed their thermal environment on average 12.8 ± 1.9 times during the test, which made them more mobile than A. diadematus, changing their thermal environment 2.7 ± 0.5 times. On the other hand, the thermal niche breadth of A. diadematus acclimated to warm temperature was wider than that of E. atrica. The female behaviour may be related to the selection of optimal conditions with regard to food availability (location for web construction), shelter and/or, in the case of E. atrica, embryonic development.

Improved mitochondrial function in salmon (Salmo salar) following high temperature acclimation suggests that there are cracks in the proverbial \u2018ceiling\u2019

Mitochondrial function can provide key insights into how fish will respond to climate change, due to its important role in heart performance, energy metabolism and oxidative stress. However, whether warm acclimation can maintain or improve the energetic status of the fish heart when exposed to short-term heat stress is not well understood. We acclimated Atlantic salmon, a highly aerobic eurythermal species, to 12 and 20 °C, then measured cardiac mitochondrial functionality and integrity at 20 °C and at 24, 26 and 28 °C (this species’ critical thermal maximum ± 2 °C). Acclimation to 20 °C vs. 12 °C enhanced many aspects of mitochondrial respiratory capacity and efficiency up to 24 °C, and preserved outer mitochondrial membrane integrity up to 26 °C. Further, reactive oxygen species (ROS) production was dramatically decreased at all temperatures. These data suggest that salmon acclimated to ‘normal’ maximum summer temperatures are capable of surviving all but the most extreme ocean heat waves, and that there is no ‘tradeoff’ in heart mitochondrial function when Atlantic salmon are acclimated to high temperatures (i.e., increased oxidative phosphorylation does not result in heightened ROS production). This study suggests that fish species may show quite different acclimatory responses when exposed to prolonged high temperatures, and thus, susceptibility to climate warming.

Extreme warm acclimation temperature alters oxygen consumption, micronucleus formation in erythrocytes, and gill morphology of rohu (Labeo rohita) fingerlings.

Experiencing the seasonal variation and rapid global warming in the tropical climate is a common phenomenon which challenged the aquatic organisms to adapt the physiology and behavior. To investigate the effect of high-temperature acclimation, we selected Indian major carp, rohu (Labeo rohita), a commercially important freshwater aquaculture species. Oxygen consumptions, micronucleus formation in erythrocytes, and gill histopathology were observed in L. rohita fingerlings acclimated at three temperatures (30, 33, and 36°C) for 30days. Results showed that the highest acclimated temperature (36°C) induced higher oxygen consumption and increased frequency of micronucleus formation in erythrocytes. Severity of different histological alterations (hyperplasia, epithelial necrosis, telangiectasis, epithelial lifting, and hypertrophy of chloride cells) in the gills was found to be increased in the highest acclimated temperature (36°C). These findings indicate the temperature induced adaptive responses and climate vulnerability in a changing environment.

Correction to: High-temperature acclimation strategies within the thermally tolerant endosymbiont Symbiodinium trenchii and its coral host, Turbinaria reniformis, differ with changing pCO2 and nutrients

Correction to: High-temperature acclimation strategies within the thermally tolerant endosymbiont Symbiodinium trenchii and its coral host, Turbinaria reniformis, differ with changing pCO2 and nutrients

High temperature acclimation alters upper thermal limits and growth performance of Indian major carp, rohu, Labeo rohita (Hamilton, 1822).

Increase in water temperature due to anthropogenic and climatic changes is expected to affect physiological functions of fish. In this study, we determined high temperature tolerance (CTmax) of a common aquacultured Indian major carp, rohu, Labeo rohita fingerlings (15.96±0.72g BW, 11.56±0.42cmTL) followed by acclimatization at three temperatures (30, 33, 36°C). To determine the CTmax, we analyzed the major hemato-biochemical indices - hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC), blood glucose levels, and erythrocytic nuclear abnormalities (ENAs) and erythrocytic cellular abnormalities (ECAs) of peripheral erythrocytes in the fish sampled at the start and end point at each acclimated temperature. Significantly decreased CTmax of the fish was found at 36°C compared to 30°C and 33°C. The fish in the highest (36°C) temperature were found with significantly lower Hb and RBC content and significantly higher WBC and blood glucose levels than that of the fishes in the lowest (30°C) temperature both at the start and end points. The highest frequencies of ENAs and ECAs were found in the highest (36°C) temperature group compared to the lowest (30°C) temperature group at both the points. We also evaluated growth performance of the rohu fingerlings reared in the three temperatures for 60 days. The growth parameters - final weight gain, percent weight gain and specific growth rate were the highest at 33°C and the lowest at 36°C. The present study revealed that the highest temperature (36°C) tested here may be hazardous to rohu and the temperature should be kept below 36°C in the aquaculture setting to avoid physiological damage and growth and production loss to the fish.

High temperature acclimation alters the emersion behavior in the crab Neohelice granulata.

An increase in environmental temperature can deleteriously affect organisms. This study investigated whether the semiterrestrial estuarine crab Neohelice granulata uses emersion behavior as a resource to avoid thermal stress and survive higher aquatic temperatures. We also examined whether this behavior is modulated by exposure to high temperature; whether, during the period of emersion, the animal loses heat from the carapace to the medium; and whether this behavior is altered by the temperature at which the animal has been acclimated. The lethal temperature for 50% of the population (LT50) was determined through 96-h mortality curves in animals acclimated at 20°C and 30°C. The behavioral profile of N. granulata during thermal stress was based on monitoring crab movement in aerial, intermediary, and aquatic zones. Acclimation at a higher temperature and the possibility of emersion increased the thermotolerance of the crabs and the synergistic effect of acclimation temperature. The possibility of leaving the hot water further increased the resistance of these animals to thermal stress. We observed that when the crab was subjected to thermal stress conditions, it spent more time in the aerial environment, unlike under control conditions. Under the experimental conditions, it made small incursions into the aquatic environment and stayed in the aerial environment for a longer time in order to cool its body temperature. The animals acclimated at 20°C and placed into water at 35°C remained in the aerial zone. The animals acclimated and maintained at 30°C (control) that were placed in water at 35°C with the possibility of emerging into hot air transited more frequently between the aquatic and aerial zones than did the animals that were put in water at 35°C with the possibility of emerging into a cooler air environment. We conclude that emergence behavior allows N. granulata to survive high temperatures and that this behavior is influenced by acclimation temperature.

Thermal plasticity in the invasive south American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae).

South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating invasive global insect pest of tomato, Solanum lycopersicum (Solanaceae). In nature, pests face multiple overlapping environmental stressors, which may significantly influence survival. To cope with rapidly changing environments, insects often employ a suite of mechanisms at both acute and chronic time-scales, thereby improving fitness at sub-optimal thermal environments. For T. absoluta, physiological responses to transient thermal variability remain under explored. Moreso, environmental effects and physiological responses may differ across insect life stages and this can have implications for population dynamics. Against this background, we investigated short and long term plastic responses to temperature of T. absoluta larvae (4th instar) and adults (24-48h old) from field populations. We measured traits of temperature tolerance vis critical thermal limits [critical thermal minima (CTmin) and maxima (CTmax)], heat knockdown time (HKDT), chill coma recovery time (CCRT) and supercooling points (SCP). Our results showed that at the larval stage, Rapid Cold Hardening (RCH) significantly improved CTmin and HKDT but impaired SCP and CCRT. Heat hardening in larvae impaired CTmin, CCRT, SCP, CTmax but not HKDT. In adults, both heat and cold hardening generally impaired CTmin and CTmax, but had no effects on HKDT, SCP and CCRT. Low temperature acclimation significantly improved CTmin and HKDT while marginally compromising CCRT and CTmax, whereas high temperature acclimation had no significant effects on any traits except for HKDT in larvae. Similarly, low and high temperature acclimation had no effects on CTmin, SCPs and CTmax, while high temperature acclimation significantly compromised adult CCRT. Our results show that larvae are more thermally plastic than adults and can shift their thermal tolerance in short and long timescales. The larval plasticity reported here could be advantageous in new envirnments, suggesting an asymmetrical ecological role of larva relative to adults in facilitating T. absoluta invasion.

Thermal Tolerance and Metabolism of Archocentrus nigrofasciatus Acclimated to a Large Daily Temperature Fluctuation Reflect its Success as an Invasive Species

Fish exhibit thermal tolerance and metabolism correlated to recent thermal history, and more studies should examine species’ responses to large fluctuations in daily temperatures. We compared thermal tolerance and metabolic responses between fish acclimated to constant temperatures and a large, daily thermal cycle of 10°C. Black Convict cichlid (Archocentrus nigrofasciatus) is a freshwater teleost native to Central America, with non‐native populations established in numerous locations. Black Convict cichlid were acclimated for two weeks to constant 20°C or 30°C, or a daily cycle of 20–30°C (“cycling group”, ~0900–1500 hrs). Following acclimation, routine metabolism (oxygen consumption, Mo2) and Critical thermal maxima/minima (CTmax/CTmin) were measured. Critical thermal limits were compared via ANOVA, with the cycling group sampled from both the daily minimum at 20°C (0900 hrs) and daily maximum at 30°C (1600 hrs). CTmax (0.3°C per degree of acclimation) and CTmin (0.4 °C per degree of acclimation) increased with acclimation. CTmax for the cycling group were 0.7°C higher when sampled from the maximum 30°C (39.3°C) of the daily cycle compared to 20°C (38.6°C). CTmin values for the cycling group were 2.2°C higher when sampled from the maximum 30°C (14.6°C) of the daily cycle compared to 20°C (12.4°C). Mo2 was measured acutely at 20°C and 30°C for each acclimation group, with the cycling group sampled from the daily minimum at 20°C (0900 hrs) and daily maximum at 30°C (1600 hrs). ANOVA showed that mass‐specific Mo2 decreased with increasing acclimation temperature for fish measured acutely at 30°C, where fish acclimated to 20°C (Mo2 = 0.329 mg/h/g) demonstrated an 84% higher Mo2 than fish acclimated to 30°C (Mo2 = 0.178 mg/h/g). Mass‐specific Mo2 also decreased with increasing acclimation temperature for fish measured acutely at 20°C, where fish acclimated to 20°C (Mo2 = 0.170 mg/h/g) demonstrated a 139% higher Mo2 than fish acclimated to 30°C (Mo2 = 0.071 mg/h/g). Mo2 was measured continually across the 24h daily thermal acclimation cycle of 20 – 30°C for all groups. Total oxygen consumption across the 24h cycle was highest for the constant 30°C group naively exposed to the cycle and lowest for the cycling group. Black Convict cichlid retains more upper thermal tolerance than lower thermal tolerance with altered thermal acclimation, and this hardy species shows metabolic compensation following high temperature acclimation (30°C) and large, daily cycling temperature acclimation (20 – 30°C). These aspects of fish thermal physiology phenotypes are reflective of a successful invasive fish species that may respond more robustly to impacts from anthropogenic climate change.Support or Funding InformationFunding was provided through startup funds to JE from CSUSM.

Growth and survival performance of Mrigal Cirrhinus mrigala fingerlings in high temperature at laboratory condition

Global warming is expected to affect the aquatic ecosystem and aquaculture industry. In the current experiment, we have observed growth and water quality of Indian major carp mrigal (Cirrhinus mrigala) exposed to three different temperature regimes, such as 30, 33 and 36°C representing T1, T2 and T3, respectively for 60 days. One hundred and twenty fish were used, kept in 6 Aquarium, and were exposed to the different temperature. Highest body weight gain and lowest feed conversion ratio (FCR) was recorded at T2. The highest specific growth rate was recorded at T2 followed by T1 and T3. The optimum temperature range for growth was 30 to 33°C. Survival at different acclimation temperatures was between 90.00±0.00, 90.0±0.00 and 75.00±0.00%, from lower to higher acclimation temperatures. Dissolved oxygen decreased and free CO2 increased significantly (P<0.05) with increasing temperature, while pH and total alkalinity significantly showed no distinct changes in any temperature conditions. On the other hand, the ammonia levels significantly increased at day 7 in 36°C. Taken altogether, this study confirmed that mrigal feel better growth at 30°C and 33°C, while high temperature is stressful to Indian major carp mrigal.
 Res. Agric., Livest. Fish.6(3): 415-420, December 2019

A new indicator of hypoxia tolerance in abalone, developed based on heart rate fluctuations

China is the largest producer and consumer of abalone worldwide, harvesting nearly 140,000 tons in 2016. Due to rising temperatures, intensive culture patterns, and other factors, hypoxia has become a serious problem for Chinese abalone aquaculture, especially in Fujian Province. A hypoxia-tolerant strain is needed for the sustainable development of abalone farming. However, it is problematic to evaluate hypoxia tolerance in abalone. Usually, the traditional analyses cause severe damages to the sampled individuals, possibly including disorders in gonad development or death and these samples could hardly be used for breeding. Here, it was found that abalone heart rates characteristically exhibited a sharp decline below a certain DO threshold, which can be referred to as the breakpoint of dissolved oxygen (BPDO). The BPDOs were sensitive to temperature – the higher acclimation temperature or experimental temperature would increase BPDO. To verify the utility of BPDO as an indicator of hypoxia tolerance in abalone, an acute stress test was conducted with 32 abalone individuals under severe hypoxia (~0.5 mg/L) and significant negative correlations between BPDO and attachment duration, and between BPDO and survival time were found. The BPDO method was advantageous, as it supported individual detection and survival, which allows the selection and retention of hypoxic-tolerant individuals for further genetic breeding. BPDOs at different temperatures also provide important references for abalone aquaculture.

Transcript-Level Analysis in Combination with Real-Time PCR Elucidates Heat Adaptation Mechanism of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) Larvae.

Tribolium castaneum (Herbst) ranks as one of the most prevalent insects in food processing and storage facilities worldwide. Heat treatment has been revisited to disinfest food processing and storage facilities due to increasingly strict regulation on chemicals. The effect of acclimation of T. castaneum larvae to sublethal high temperatures of 36 and 42℃ for 10 h on their heat adaptation was investigated, and transcript-level analysis combinating with real-time PCR (RT-qPCR) was applied for elucidating the heat adaptation mechanism of T. castaneum larvae. Short-term sublethal high temperature acclimation could greatly enhance the thermal adaptability in T. castaneum larvae. In total, 575, 875, and 1017 differentially expressed genes (DEGs) were, respectively, determined in comparisons between the 28 and 36℃ treatments, the 28 and 42℃ treatments, and the 36 and 42℃ treatments. Fifty-three and 96 genes were commonly up- and down-regulated in both the 36 and 42℃ treatments relative to 28℃, respectively. The results of RT-qPCR analysis further confirmed the RNA-seq analysis. The current results are in favor of enhancing the insecticidal effectiveness of extreme high temperature treatment and elucidating the heat adaptation mechanism in T. castaneum larvae.

Expression of thermal tolerance genes in two Drosophila species with different acclimation capacities.

Heat tolerance increases at higher acclimation temperatures in D. melanogaster, but not in D. subobscura. The two species represent separate lineages of the subgenus Sophophora of Drosophila with contrasting tropical African and temperate Palearctic evolutionary histories. D. melanogaster has five copies of the inducible hsp70 gene distributed in two clusters, named A (with two copies) and B (three copies), while D. subobscura has only two copies arranged similarly to cluster A of D. melanogaster. The hsp70s of the two species also differ in their cis-regulatory regions, with D. melanogaster exhibiting features of a faster and more productive promoter. We predicted that the interspecific variation in acclimation capacity of heat tolerance is explained by evolved variation in expression of the major group of heat shock proteins. To test this prediction, we compared basal levels of gene expression at different developmental temperatures within each of the two species. Furthermore, we explored the heat hardening dynamics by measuring the induction of gene expression during a ramping assay. The prediction of a stronger heat shock protein response in D. melanogaster as compared to D. subobscura was confirmed for both long-term acclimation and short-term hardening. For D. melanogaster the upregulation with temperature ramping ranged from less than two fold (hsp26) to 2500 fold (hsp70A) increase. In all cases induction in D. melanogaster exceeded that of D. subobscura homologs. These differences correlate with structural differences in the regulatory regions of hsp70, and might explain differences in acclimation capacity among species. Finally, in D. melanogaster we found an indication of an inverse relationship between basal and induced levels of hsp70A and hsp83 expression, suggesting a divergent role for thermal adaptation of these genes at benign and stressful temperatures, respectively.

Effects of developmental acclimation on fitness costs differ between two aphid species

Most ectotherms are able to increase their tolerance to heat stress via the acclimation response. However, there is ongoing debate about whether the acclimation response is associated with fitness costs, and what factors can affect the consequences of acclimation are still unclear. To elucidate this, we sought to determine whether fitness costs varied with acclimation conditions in two cereal aphids, Sitobion avenae and Rhopalosiphum padi. Thus, the basal and inducible thermal tolerances (maximum critical temperature [CTmax]) and fitness traits (proportion of adult emergence, adult longevity, fecundity, and population parameters) of adult aphids were measured under three conditions of developmental acclimation: 1) 22 °C constant temperature (no acclimation), 2) 22 °C + 34 °C for 2 h per day (low daytime temperature), and 3) 22 °C + 38 °C for 2 h per day (high daytime temperature). We found that the thermal tolerances of both species were significantly higher following developmental acclimations, where higher basal and inducible thermal tolerances were observed in R. padi than in S. avenae. Low daytime temperature acclimation conditions (34 °C) resulted in negligible reproductive costs and improved the intrinsic rates of population increase in both species. In contrast, substantial fitness costs were detected in both species in response to high daytime temperature acclimation (38 °C), especially for S. avenae. Our results indicate that the effects of acclimation conditions on fitness costs differ between the two aphid species. These findings will not only enhance our understanding of species dynamics in the context of climate change but could also potentially improve pest control efforts.

Comparison of the activities of photosystem II of four table grapevine cultivars during high-temperature stress

High-temperature stress influences the growth and development of grapevines, and plant responses to this stress vary between laboratory and natural conditions. In the present study, the responses to high-temperature stress in four grapevine cultivars (‘Summer Black’, ‘Zuijinxiang’, ‘Hupei1#’, and ‘Shenfeng’) were studied by comparing chlorophyll a fluorescence and the levels of heat-shock protein 21 (HSP21) after exposure to control (35 °C in controlled laboratory conditions or at 37 °C in a greenhouse with naturally fluctuating temperatures) and high-temperature stress treatments (45 °C in laboratory conditions or 42 °C in the field conditions). Leaf water loss in ‘Summer Black’ was less than that in the three other cultivars after treatment at 45 °C. Some parameters (ΨEo, Wk, RCQA, and Mo) of photosystem II (PSII) activity were altered in ‘Shenfeng’, ‘Zuijinxiang’, and ‘Hupei1#’, but were unaltered in ‘Summer Black’ after treatment at 45 °C. Other parameters (maximum photochemical efficiency (Fv/Fm), performance index on absorption basis (PIABS), ΦPo, ΦEo, and HSP21 levels) were altered in ‘Summer Black’, but to a lesser extent than in the three other cultivars under high-temperature stress. Unlike ‘Summer Black’, extreme injury owing to leaf water loss to ‘Shenfeng’, ‘Zuijinxiang’, and ‘Hupei1#’ could be explained by disruption of PSII activity. Furthermore, there were the observed differences in PSII activity between in laboratory and field conditions, which could be considered as the mechanisms for high-temperature acclimation and other environment factors.

Superior basal and plastic thermal responses to environmental heterogeneity in invasive exotic stemborer Chilo partellus Swinhoe over indigenous Busseola fusca (Fuller) and Sesamia calamistis Hampson

AbstractLepidopteran stemborers are the most destructive insect pests of cereal crops in sub‐Saharan Africa. In nature, these insects are often exposed to multiple environmental stressors, resulting in potent impact on their thermal tolerance. Such environmental stressors may influence their activity, survival, abundance and biogeography. In the present study, we investigate the effects of acclimation to temperature, starvation and desiccation on thermal tolerance, measured as critical thermal limits [critical thermal minima (CTmin) and maxima (CTmax)] on laboratory‐reared economic pest species Chilo partellus Swinhoe (Lepidoptera: Crambidae), Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae) using established protocols. Low temperature acclimation results in improved CTmin for B. fusca and C. partellus, whereas high temperature acclimation enhances the same trait for B. fusca and S. calamistis. Similarly, high temperature and starvation pretreatment improve CTmax for C. partellus relative to S. calamistis and B. fusca. In addition, starvation and desiccation pretreatments improve CTmin for all stemborer species. Furthermore, rapid cold‐hardening (RCH) enhancs CTmin for B. fusca and C. partellus, whereas rapid heat‐hardening (RHH) improves the same trait for C. partellus. However, RCH and RHH impair CTmax for all stemborer species. These findings show differential thermal tolerances after exposure to heterogeneous environmental stress habitats. Chilo partellus, of exotic origin, shows a higher magnitude of basal thermal tolerance plasticity relative to the indigenous African species S. calamistis and B. fusca. This indicates that C. partellus may have a fitness and survival advantage under climate‐induced heterogeneous environments, and also have a greater chance for geographical range expansion and invasion success compared with the indigenous B. fusca and S. calamistis.

Thermal plasticity potentially mediates the interaction between host Chilo partellus Swinhoe (Lepidoptera: Crambidae) and endoparasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) in rapidly changing environments.

Increasing climatic average temperatures and variability elicit various insect physiological responses that affect fitness and survival and may influence subsequent trophic interactions in agroecosystems. In this background, we investigated short- and long-term plastic responses to temperature of the laboratory-reared stemborer Chilo partellus and its larval endoparasitoid Cotesia flavipes. Rapid cold- and heat-hardening effects in C. partellus larvae, pupae and adults and C. flavipes adults were highly significant (P < 0.001). High-temperature acclimation improved critical thermal limits and heat knockdown time in C. partellus larvae and C. flavipes adults, respectively. Low-temperature acclimation enhanced the supercooling point in C. flavipes and the chill coma recovery time in both C. partellus larvae and C. flavipes adults. The results of this study suggest that thermal plasticity may enhance the survival of these two species when they are subjected to lethal low and high temperatures. However, C. partellus appeared to be more plastic than C. flavipes. These results have three major implications: (1) C. partellus may inhabit slightly warmer environments than C. flavipes, suggesting a potential mismatch in biogeography; (2) host-parasitoid relationships are complex and are probably trait dependent, and (3) host-parasitoid differential thermal plastic responses may offset biocontrol efficacy. These results may help inform biocontrol decision making under conditions of global change. © 2017 Society of Chemical Industry.

The proteomic response of the reef coral Pocillopora acuta to experimentally elevated temperatures.

Although most reef-building corals live near the upper threshold of their thermotolerance, some scleractinians are resilient to temperature increases. For instance, Pocillopora acuta specimens from an upwelling habitat in Southern Taiwan survived a nine-month experimental exposure to 30°C, a temperature hypothesized to induce stress. To gain a greater understanding of the molecular pathways underlying such high-temperature acclimation, the protein profiles of experimental controls incubated at 27°C were compared to those of conspecific P. acuta specimens exposed to 30°C for two, four, or eight weeks, and differentially concentrated proteins (DCPs) were removed from the gels and sequenced with mass spectrometry. Sixty unique DCPs were uncovered across both eukaryotic compartments of the P. acuta-dinoflagellate (genus Symbiodinium) mutualism, and Symbiodinium were more responsive to high temperature at the protein-level than the coral hosts in which they resided at the two-week sampling time. Furthermore, proteins involved in the stress response were more likely to be documented at different cellular concentrations across temperature treatments in Symbiodinium, whereas the temperature-sensitive host coral proteome featured numerous proteins involved in cytoskeletal structure, immunity, and metabolism. These proteome-scale data suggest that the coral host and its intracellular dinoflagellates have differing strategies for acclimating to elevated temperatures.